I'm reading a manga and two people are having a conversation about a secret rendezvous (not sure yet if it's a rendezvous between the two people speaking or the people they are speaking about), when the man says:

今ごろお前の隣の部屋で / ヤリまくりだ

I believe the first part says "About this time at your neighbor's place," but I don't know what the second part means. I've looked it up on jisho.org and have inputted it into a few translators and nothing relevant comes up. I've even parsed it thinking that as 2 separate words (ヤリ＋まくり) something would ring a bell. The slash is where the sentence was broken up in the manga.

Please tell me what ヤリまくり means and if I've correctly translated the first part of the sentence as well.

omg, thanks! I thought it had to do with "doing the dirty" based on the context of the conversation, but I really wanted to make sure since I hadn't come across the phrase before.
– RoseJul 14 '16 at 3:33